Spesiasi Aluminium Terlarut dan Sifat Kimia Ultisol yang Diameliorasi dengan Dolomit dan Lignit-Teraktivasi

Phytotoxicity of soil aluminum (Al), both directly to the plant growth as well as indirectly through the increase of soil potential acidity, is closely related to the occurrence of various soil soluble-Al species. Amongst them, Al3+ and monomeric-Al species are the primary causes of Al phytotoxicity in soils with high Al content. This study was aimed to evaluate the effects of soil amelioration with dolomite and base-activated lignite (BAL) on changes in soluble-Al species and other soil chemical properties, and vegetative growth of soybean (Glycine max Merr) on Ultisol of Jasinga (Al-dd 16,03 cmol(+)/kg). A green house experiment was conducted by applying a Completely Randomized Design with dolomite and BAL amelioration as the treatments, each with three levels of repectively 0, 1, 1,5 x exchangeable-Al and 0, 2,5, 5 tons BAL ha-1, and three replications. The ameliorants were incubated at field capacity of soil moisture content for one week before planting soybean for one month. Soil soluble-Al speciation was carried out using colorimetric aluminon method to determine concentrations of total soluble-Al, monomeric-Al, and polymeric-Al species. Monomeric-Al were further speciated into inorganic monomeric-Al and organic monomeric-Al species. The results revealed that only dolomite amelioration that significantly increased soil pH-H2O, pH-KCl, Ca- dd, Na-dd, and decreased exchangeable-Al concentration, except for those of all soluble-Al species that only showed a decreasing trend. Soil exchangeable-Al that was negatively and significantly correlated with soybean measure parameters were plant height, root length, total roots and shoots wet and dry weights, as well as Ca concentration. These results indicated that soil Al phytotoxicity evaluation could be relied on the result of routine analysis on soil exchangeable-Al concentration. Keywords: exchangeable-Al, inorganic monomeric-Al, organic monomeric-Al, polymeric-Al

Deteksi Potensi Fitotoksisitas Aluminium Pada Tanah Toksik Di Lahan Reklamasi Kawasan Hutan Dengan Bioassay Sorgum

Aluminium (Al) phosphotoxicity is the most common constraint in acidic soil. Information on potential Al phytotoxicity is required in revegetation planning, monitoring of this information is generally done through laboratory analysis procedure in the laboratory that requires high cost and time. The purposes of this study were to test the method of quick detection of Al phytotoxicity with sorghum bioassay. Soil samples taken from post-gold mining land in Bolaang Mongondow Regency of North Sulawesi Province were analyzed for soil physical and chemical properties then planted with numbu varieties of sorghum with complete randomized design, sorghum growth performance response and its correlation with soluble Al and pH were analyzed and then the symptoms occured from Al-toxicity on sorghum were observed. Sorgum responds to Al-toxicity by showing symptoms of shortening and thickening of the roots and stunted growth performance. Sorghum growth performance has significant negative correlation with soluble Al concentration on soil, and soil acidity showed a stronger correlation. Al-phytotoxicity symptom in sorghum at pH below 3.7 begins to be clearly visible and easily observed, this distinct appearance difference makes sorghum potential to be used as bioindicator to detect Al- phytotoxicity on the soil.Keywords: Aluminium phytotoxicity, sorghum, post-mining revegetation

Amelioration of alkaline phytotoxicity by lowering soil pH

Highly alkaline soils (pH >9) may adversely affect agricultural crop productivity. At pH >9.2, aluminium (Al) phytotoxicity may further retard plant development. Most alkaline soils have little alkaline buffering capacity, making it feasible to use acid to lower soil pH to <9.2. Many methods of lowering soil pH have been trialled; however, little research has been done on their relative effectiveness and longevity. Methods trialled in this study as means of lowering soil pH were chemical additives (gypsum), organic additives (glucose, molasses, horse manure, green manure, humus) and leguminous plants. Gypsum was also used in conjunction with plants to determine any synergistic effects of combining treatments. All ameliorants trialled except humus and horse manure proved effective at lowering soil pH to <9.2. The reduction achieved with biological amendments was temporary, with pH returning to pre-amendment levels over the course of the study. Gypsum was most effective amendment for lowering soil pH and sustaining the lowered pH level. The use of plants to lower soil pH, in conjunction with gypsum to sustain the lowered pH, may be an effective and economic method of remediating Al phytotoxicity in alkaline soils.

Validation of an Alt locus for aluminium tolerance scored with eriochrome cyanine R staining method in barley cultivar Honen (Hordeum vulgare L.)

Aluminium (Al) phytotoxicity is one of the major constraints for barley (Hordeum vulgare L.) production on acid soils. Genetic variation for Al tolerance is present in barley germplasm. Previous studies have shown that Al tolerance in cv. Dayton and WB229 is controlled by a single locus on 4H. The present study was conducted to investigate the genetic control of Al tolerance in Japanese barley cv. Honen, and validate the linkage relationship between the Al tolerance locus and the molecular markers established previously. An F3 progeny representing 94 F2s from the cross of F6ant28B48-16 (Al sensitive) × Honen (Al tolerant) was evaluated for Al tolerance by staining roots with eriochrome cyanine R. A single Al tolerance locus Alt was validated on the long arm of chromosome 4H in Honen. Single sequence repeat (SSR) markers Bmag353 and HVM68 flanked the Alt locus at a distance of 1.6 ± 0.9 and 5.1 ± 1.7 cM, respectively. Our results have shown that the linkage between SSR markers and the Al tolerance locus can be used to characterise the ‘unknown source’ for Al tolerance.

Alleviation of aluminium phytotoxicity on soybean growth by organic anions in nutrient solutions

The effect of aluminium (Al) phytotoxicity on the growth of soybean (Glycine max (L.) Merr.) cv. ‘Forrest’ in nutrient solutions (pH 4.25) and its alleviation by organic anions has been investigated. Both 100 and 500 µM Al caused significant reduction in root and shoot lengths and root dry weights over 15 days. Citrate, oxalate, tartrate, malate, malonate and lactate at 1000 µM and humic acid at 1 g L-1 were used to alleviate phytotoxicity caused by the presence of 500 µM Al. The effectiveness of the organic anions in alleviating Al phytotoxicity, measured by the change in root length, was in the order oxalate > citrate ≈ tartrate ≈ malate > malonate >> lactate. Humic acid at 1 g L-1 proved almost as effective as 1000 µM citrate. When the remaining fraction of phytotoxic aluminium was measured by the aluminon method and the results combined with calculated values obtained from stability constant data, the order of effectiveness of complexation was citrate > oxalate > tartrate ≈ malate ≈ malonate >> lactate. It was concluded that benefits other than from simple complexation of phytotoxic aluminium were provided by the organic anions. Three of the anions were also used at different concentrations; these were citrate and oxalate (at 250, 500 and 1000 µM) and humic acid (at 0.01, 0.1 and 1.0 g L-1 ). For citrate and oxalate, it was found that the concentration of the organic anion must be at least that of the Al to reduce phytotoxicity significantly, and twice as much oxalate as citrate was required to achieve the same reduction in phytotoxicity.